The present invention relates to a device and method for repairing pipe, such as underground sewer pipe and the like.
Prior methods for repairing damaged pipelines include moving a liner tube impregnated with a liquid material capable of curing and hardening to a position within the pipe where the damaged portion is located. The liner tube is urged in an outward radial direction into contact with the pipe being repaired and the liquid material impregnating the liner tube is permitted to cure and harden. The liner tube is installed by pulling, pushing or everting the liner into the host pipe. Once the liner tube is positioned within the host pipe, it is pressurized, causing the liner to press against the interior wall of the host pipe, and the liner is cured by applying heat, such as steam or hot water. These liners can also be cured at ambient temperatures by a chemical mixture which generates an exothermic reaction or by ultraviolet light. The liner tube forms an interior liner in the pipe for the pipeline being repaired. Such a process is known as cured-in-place pipelining.
On some occasions lateral pipes are connected to main pipes. Often damage occurs at the junction between the lateral pipe and the main pipe. T-shaped or Y-shaped liner tubes have been utilized to fit within the junction between the lateral and main pipes. Liner tubes form a T-shaped or Y-shaped liner after hardening to the interior of the junction between the pipes.
An example of a T-shaped main/lateral liner installed in a pipeline is shown in FIG. 1. A main liner tube 10 and a lateral liner tube 12 form a one-piece lining along the interior walls of the main sewer pipe 14 and the lateral sewer pipe 16. Each of the liner tubes includes a felt lining portion 18, 20 and a plastic coating 22, 24.
A common material used for cured-in-place pipelining is a tube made of needle-punched felt with a coating on one surface. The coating is made of an impervious thermoplastic film, such as polyethylene (PE), polyvinyl chloride (PVC) or thermoplastic polyurethane (TPU). These plastic films must be flexible in order to negotiate bends in the pipeline and allow the lining tube to be everted into the pipeline under a fluid pressure. Most coatings have a thickness of approximately 15 mils.
The coating on the liner is used to help ensure a leak-free tube. Even though the liner tube is impregnated with resin and is cured as a one-piece continuous lining, there are small canals found in cured-in-place pipe that allow leakage. A coating impervious to water is therefore essential for creating a non-leaking cured-in-place pipe. However, these coatings are made of a thin plastic film, which over time wear away due to abrasion from water flow, silt and cleaning tools. Some of the coating materials are even water soluble, such as an ester grade TPU. The pipelining industry generally requires that the liners provide a minimum service life of 50 years. Service life is reduced when the film coatings are worn away as leakage occurs.
If the liner is to be everted into the host pipe, the coating on the liner is initially on the outside of the tube. Resin is introduced into the tube, which allows the felt liner to be impregnated with a liquid curable resin. The coating contains the resin within the tube. Once the liner is everted, the coating becomes the interior surface of the liner tube and the resin impregnable liner is on the outside and can be pressed against the interior of the host pipe.
A main/lateral lining includes lining the lateral pipe and a short section of the main pipe. An important part of the main/lateral liner is the main liner portion and its connection to the lateral lining tube. One method of installing a main/lateral liner is to move the liner assembly through the main pipe until the assembly is aligned with the opening to the lateral pipe. A one-piece main/lateral bladder is used to inflate the main liner and evert the lateral liner, as shown in U.S. Pat. No. 6,039,079. The main liner of the main/lateral liner assembly is inflated by the action of a main bladder, pressing the main lining against the interior of the main pipe. The main liner may be stitched along its longitudinal edges to form a tube or may be formed by overlapping a sheet of material. The lateral lining tube is everted into the lateral pipe by action of the bladder assembly.
Because lateral pipes are smaller in diameter than the main pipe and lateral pipes often have bends, the eversion process for inserting the lateral lining tube into the lateral pipe requires a much higher fluid pressure than what is required to simply inflate the main liner. However, when using a one-piece main/lateral bladder assembly, the high pressure required to evert the lateral liner is also the same pressure being applied to the main liner.
When a resin impregnated tube is pressurized and pressed against the interior of the host pipe, resin migrates into open joints and fractures in the pipe. Resin migration is a positive attribute of the cured-in-place pipelining process. Lateral lining tubes are made from a flexible felt-like material that is soft and elastic so as to evert into small diameter pipe, such as 4-6 inch diameter pipe. However, when higher pressures are required to evert the lateral lining tube into the lateral pipeline, this pressure squeezes the flexible tube, causing the main/lateral liner assembly near the juncture between the main and lateral liners to become thin with insufficient wall thickness for the desired design calculations. This thinning of the resin absorbent lining is illustrated in FIG. 2. Maintaining sufficient wall thickness and resin volume of the liner is essential to meeting the minimum physical properties of the cured-in-place lining.
There is therefore a need in the art for a device and method of renewing a pipeline that achieves good resin migration, yet controls the thickness of the liner tube wall regardless of the process used to install the liner. There is also a need in the art for a new liner that resists compression, maintains sufficient wall thickness, is durable, and effectively seals any cracks in the damaged section of pipe. There is also a need in the art for a new liner having a substantially impervious layer, providing a long service life leak-free lining.